The present invention relates to integrated circuit gates, and more particularly to an ECL supergate circuit to provide high speed communication between circuit boards in a semi-compatible environment.
Electronic devices, such as test instruments, contain a plurality of printed circuit or integrated circuit cards, each having a complex electronic circuit. Signals from these cards have to be communicated to other cards to be combined with other signals or for other signal processing. Usually these cards are connected together by a backplane, which is a circuit board having a plurality of interconnected connectors to which the cards are connected. Each card has its own power supply source which may vary from card to card. A typical circuit for communicating from one card to another across the backplane would provide for a differential input, a single ended input and a differential output. Current integrated circuits require the combination of two different integrated circuits, such as the 100114 Quintuple Differential Line Receiver followed by the 100102 Quintuple Two-Input OR/NOR Gate with Common Enable Differential In--Differential Out manufactured by Signetics Corporation of Sunnyvale, Calif. The typical delay for a signal through these gates is approximately 0.65-2.2 nsec plus 1.0-1.95 nsec for a total delay of 1.65-4.15 nsec with a difference in the amount of delay between the differential input and single ended input at the differential output. For communication rates of 250 MHz and above this propagation delay through the gates is unacceptable.
What is desired is a supergate which provides communication between semi-compatible cards with a propagation delay compatible with high speed communications.